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Sheathing for Wet Offroad Conditions

Practical Motorsport Wiring - Club Level

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Hey guys, Im building a 1990 Ford Bronco and redoing ALL of the wiring.

In this process, I want to still mosty follow OE wiring, but in some cases modify it to be more conscious of high-water i situations. (1 to 1.25 meters high)

In my quest for this, Im coming to a debate with myself......how do i make the wiring harnesses more suitable for these conditions?

My thoughts are Raychem DR25 with SCL boots everywhere i can.....BUT....there is also the thought that if water does get in (submerging the vehicle) that it will likely be trapped because the SCL doesnt COMPLETELY seal everything...i could go as far as shooting some potting compound into the branch joints, i suppose...

So that would leave expandable braid as the next option.......but i just see that getting clogged up with mud.

Anyone out there done something like this? What would be your choice and why?

I myself am still thinking Raychem DR25/SCL and boot any connectors i can get away with........

Great question Zach!

With electronics and connectors that are sufficiently sealed, proper connector boot lips, my first thought is to try and achieve a full seal across the system with boots and sheathing rather than operating as if intrusion is unavoidable, making letting water that gets in back out important, but I am NOT a harness building expert. I don't know best practice, don't have the answer for you, but look forward to hearing what those more knowledgeable on the subject have to say.

Imo you're better off using heat shrink boots and sealing with an epoxy like RT125 then SCL. SCL is really great but the resin inside it doesn't flow out the same way the epoxy can and does.

Connector choice is also going to matter here, not all are built the same. DT and DTM carry different IP ratings. You'll have to decide how far you want to take it, as most OEM connectors are not meant or rated for submersion, just splash or in some cases water spray.

Braided loom will usually trap and hold water in my experience. It will dry out eventually, leaving salt and other deposits inside. Also loves clinging onto oil and mud, there's a reason OEM's don't use it.

If I was gonna treat this like a submarine I would opt for DR25, heat shrink boots, epoxy and IP68 connectors everywhere, but that gets expensive somewhat quickly.

Another suggestion to me on another platform was to observe what Jet Ski manufacturers (such as Sea Doo and Yamaha) are doing with their harnesses, because those are watercraft.

The thing i have noticed in pictures is that im not sure that they really did much for water intrusion besides properly sealed connectors. This, I am thinking is because the body of the watercraft HAS to be watertight, in order to avoid obvious sinking and user injury risks....

It HAS also been brought to my attention, that instead of open barrel splices, as an alternative, i could go for Deutsch Sealed Bus Bars for the major power splices. This employs a threaded stud terminal and a 12 pin deutsch connection.

I have been looking at the RT125 also, yes.

I agree most OE connectors are not likely rated for submersion, thats why I am playing with the idea of keeping as much of the wiring as I can A) high enough that it wont be affected and B) possibly running some things INSIDE the truck. That opens up the subject of there being more holes in the truck body, but if strategically placed i shouldnt have too much issue.

BUT, i would really like to keep the factory routing if possible.

I think some of the main concerns here are:

Transmission & associated components

Crank sensor connector

Winch (disconnected during water crossing)


ABS system (RABS.....debated on deleting it but it is also the brake proportioning valve, although there are aftermarket alternatives to that. This is kind of a low priority item when offroad)

Most of the engine wiring would be above water, except one of the most important pieces....the crank sensor 🙃

There may be "marine" rated fittings you can use, too, as another option?

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